Knowing one side's plans isn't enough. Alhammarret needs intel from both sides for a successful arbitration, so you're off again. You run into more troops than you were expecting. Someone important must be visiting the camp, which raises the challenge and the potential reward.
The Ampryn Core Soldiers have a Soldier tribal deck with a focus on swarming you down. Fortunately for you, the four copies of Angel's Mercy in their deck have nothing to do with that strategy; you can just ignore them completely since you win by stabilizing and then attacking evasively.
Watch out for Glorious Charge from the opponent. For example, you may want to block a 2/1 Elite Vanguard rather than a 2/2 Glory Seeker with your 2/3 Blind Phantasm so you at least still trade if the opponent plays Glorious Charge. Similarly, Turn the Tide can have a powerful effect in this matchup, allowing your creatures to engage the opposing creatures in combat while surviving themselves.
Good Cancel targets are Captain of the Watch and combat tricks (Glorious Charge or Show of Valor). Enlistment Officer can be a good target as well if you're getting swarmed, but its effect isn't very spectacular if you have board control, since you can easily deal with the 2/3 and the couple of small creatures it's likely to get for your opponent.